Coronavirus explained: How it differs from a regular flu

The spread of coronavirus continues to raise fears around the world, but is the threat as serious as it seems?

The World Health Organisation has stopped short of declaring the outbreak "a public health emergency of international concern", but the number of overseas cases continues to grow and 106 people have now died, mostly in China.

Professor John McBride, an infectious diseases physician at James Cook University in Queensland, said there was an information vacuum at the moment so it was difficult to understand the true severity of the virus, but it seemed more deadly than influenza.

"If it was no worse than the common cold, we probably would not be terribly concerned," he said. "But about 25 per cent of people infected so far are getting severe illness and require hospitalisation. This is higher than influenza and much higher than the common cold, hence the international concern."

Coronavirus_explainer

While the symptoms of the new coronavirus appear similar to an ordinary cold or flu, the virus can cause pneumonia, which has been deadly in some cases. It has spread to a dozen countries including Japan, the US and Sri Lanka.

Prof McBride said a common cold type of infection would likely not even have been identified as there are hundreds of viruses that cause colds, but the cluster of severe respiratory illness must have been significant enough for investigation.

"Clearly, it's significant clinically enough to raise people's concerns," he said.

The coronavirus family includes the common cold as well as viruses that cause more serious illnesses, such as the SARS outbreak and Middle Eastern respiratory syndrome, or MERS, which is thought to have originated from camels.

Prof McBride said the death rate of the new coronavirus was originally estimated at just under 5 per cent, and this was worse than the flu.

According to the latest Australian Influenza Surveillance Report for the 2019 flu season, there were 812 influenza-associated deaths up until October 6. This made up 0.27 per cent of the 298,120 laboratory-confirmed notifications of influenza reported to Australian authorities.

This compares to the coronavirus, with latest numbers suggesting 106 people (2.3 per cent) have died out of 4515 known cases.

Prof McBride said it appeared coronavirus was more severe than influenza, although it may not be worse than severe acute respiratory syndrome (SARS), which originated in China and killed nearly 800 people globally in 2002 and 2003.

"The difference between coronavirus and SARS is that SARS was not that infectious, it was transmitted mostly within hospitals," Prof McBride said.

This made it easy to get on top of once authorities understood how it was being passed on.

"This new virus seems to be more community-spread, so it will be more difficult to contain and control without the control of the co-operation of the general public," he said.

However, the transmission of the virus is under question after China's National Health Commission Minister Ma Xiaowei revealed on Sunday it was possible for people to spread coronavirus before they had symptoms.

The minister said the incubation period for the virus could range from one to 14 days, and the virus was infectious during incubation.

Australian authorities have a different view, according to Tanya Sorrell, professor of infections diseases at University of Sydney and director of the Centre for Infectious Diseases at Westmead Hospital.

She said authorities were "really surprised" at the Chinese announcement, and investigations by Australian authorities had come up with a different conclusion.

"If people were infectious when they're not symptomatic we would expect a lot more cases outside of China," she told ABC radio program RN Breakfast.

"It appears as though the announcement was made in a political setting based on an individual patient who we believe actually had mild symptoms, who was not asymptomatic, so it's not verified and we're very sceptical about it."

Prof Sorrell said patients were unlikely to be infectious unless they had symptoms.

"This is unlike influenza when you're maximally infectious before you develop symptoms, so it's much harder to track people," she said.

Where does this end?

The WHO is due to meet again on Thursday in Geneva to consider whether to declare a public health emergency, but Prof McBride does not know whether it would make much of a difference.

"It's hard to imagine how much stronger the response could get," he said. "I think it's been a quite aggressive response and, in the context, an appropriate response."

A WHO designation would have required countries to step up the international response. It can increase resources to fight a threat but that can also cause trade and travel restrictions and other economic damage, making the decision politically fraught.

During the SARS outbreak, air passenger demand in Asia plunged 45 per cent.

China has already placed travel restrictions over much of Hubei province, which is home to nearly 60 million people, and the city of Wuhan is in virtual lockdown. There are severe limits on movement in place in several other Chinese cities.

The Chinese Government has also extended the Lunar New Year holiday in a bid to stop the spread of the disease.

Prof McBride said WHO may step in if there was more widespread transmission of the virus between people outside of China and if pockets of infections were appearing suddenly.

"As long as public health officials can trace the person-to-person spread and react accordingly, there's hope that the disease can be contained," he said.

A clear chain of transmission means that authorities can advise those who are sick to wear a mask and avoid contact with others. This can interrupt transmission of the disease.

"We don't know what it's going to be like a year down the track. If the virus does continue to spread and become part of the landscape, then a vaccine would be useful," Prof McBride said.

Vaccines take time to develop, and in the case of the Zika virus, for example, the infection become less aggressive and so the vaccine was never widely distributed.

Prof McBride said the development of other drugs and therapeutic medication to combat the virus was also very important.

He believes travel to China in the immediate future would continue to be affected, and this could also impact tourism in other countries with poorer healthcare, especially if several cases suddenly came to light.

"We do rely on openness about transmission. As soon as any government tried to hide things, that would be very damaging," he said.

"What this requires more than anything is good communication between authorities and the public. People need to be trusting and not fearful about what happens if they go to the doctor.

"As long as we are open and transparent about the risk and advisability of seeking medical attention, we should be okay."